Company Quick10K Filing
CNA Financial
Price49.19 EPS2
Shares273 P/E21
MCap13,409 P/FCF14
Net Debt2,338 EBIT904
TEV15,747 TEV/EBIT17
TTM 2019-09-30, in MM, except price, ratios
10-K 2020-12-31 Filed 2021-02-09
10-Q 2020-09-30 Filed 2020-11-02
10-Q 2020-06-30 Filed 2020-08-03
10-Q 2020-03-31 Filed 2020-05-04
10-K 2019-12-31 Filed 2020-02-11
10-Q 2019-09-30 Filed 2019-10-28
10-Q 2019-06-30 Filed 2019-08-05
10-Q 2019-03-31 Filed 2019-04-29
10-K 2018-12-31 Filed 2019-02-13
10-Q 2018-09-30 Filed 2018-11-05
10-Q 2018-06-30 Filed 2018-07-30
10-Q 2018-03-31 Filed 2018-04-30
10-K 2017-12-31 Filed 2018-02-14
10-Q 2017-09-30 Filed 2017-10-30
10-Q 2017-06-30 Filed 2017-07-31
10-Q 2017-03-31 Filed 2017-05-01
10-K 2016-12-31 Filed 2017-02-15
10-Q 2016-09-30 Filed 2016-10-31
10-Q 2016-06-30 Filed 2016-08-01
10-Q 2016-03-31 Filed 2016-05-03
10-K 2015-12-31 Filed 2016-02-17
10-Q 2015-09-30 Filed 2015-11-03
10-Q 2015-06-30 Filed 2015-08-04
10-Q 2015-03-31 Filed 2015-05-05
10-K 2014-12-31 Filed 2015-02-23
10-Q 2014-09-30 Filed 2014-11-04
10-Q 2014-06-30 Filed 2014-08-04
10-Q 2014-03-31 Filed 2014-04-29
10-K 2013-12-31 Filed 2014-02-19
10-Q 2013-09-30 Filed 2013-10-29
10-Q 2013-06-30 Filed 2013-07-30
10-K 2012-12-31 Filed 2013-02-21
10-Q 2012-09-30 Filed 2012-10-30
10-Q 2012-06-30 Filed 2012-07-31
10-Q 2012-03-31 Filed 2012-05-01
10-K 2011-12-31 Filed 2012-02-21
10-Q 2011-09-30 Filed 2011-11-01
10-Q 2011-06-30 Filed 2011-08-02
10-Q 2011-03-31 Filed 2011-05-03
10-K 2010-12-31 Filed 2011-02-22
10-Q 2010-09-30 Filed 2010-11-02
10-Q 2010-06-30 Filed 2010-08-03
10-Q 2010-03-31 Filed 2010-05-03
10-K 2009-12-31 Filed 2010-02-23
8-K 2021-02-08 Earnings, Exhibits
8-K 2020-12-30 Enter Agreement, Regulation FD, Exhibits
8-K 2020-11-02
8-K 2020-08-11
8-K 2020-08-10
8-K 2020-08-03
8-K 2020-07-15
8-K 2020-05-04
8-K 2020-04-29
8-K 2020-03-06
8-K 2020-02-25
8-K 2020-02-10
8-K 2019-12-19
8-K 2019-10-28
8-K 2019-08-05
8-K 2019-05-01
8-K 2019-04-29
8-K 2019-04-24
8-K 2019-02-11
8-K 2018-12-03
8-K 2018-11-05
8-K 2018-09-05
8-K 2018-08-01
8-K 2018-07-30
8-K 2018-04-30
8-K 2018-04-26
8-K 2018-04-25
8-K 2018-04-06
8-K 2018-02-12

CNA 10K Annual Report

Part I
Item 1. Business
Item 1A. Risk Factors
Item 1B. Unresolved Staff Comments
Item 2. Properties
Item 3. Legal Proceedings
Item 4. Mine Safety Disclosures
Part II
Item 5. Market for Registrant's Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities
Item 6. Selected Consolidated Financial Data
Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations
Item 7A. Quantitative and Qualitative Disclosures About Market Risk
Item 8. Financial Statements and Supplementary Data
Item 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure
Item 9A. Controls and Procedures
Item 9B. Other Information
Part III
Item 10. Directors, Executive Officers and Corporate Governance
Item 11. Executive Compensation
Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters
Item 13. Certain Relationships and Related Transactions, and Director Independence
Item 14. Principal Accounting Fees and Services
Part IV
Item 15. Exhibits, Financial Statement Schedules
EX-21.1 q42020cnaex211.htm
EX-23.1 q42020cnaex231.htm
EX-31.1 q42020cnaex311.htm
EX-31.2 q42020cnaex312.htm
EX-32.1 q42020cnaex321.htm
EX-32.2 q42020cnaex322.htm

CNA Financial Earnings 2020-12-31

Balance SheetIncome StatementCash Flow
655239261302012201420172020
Assets, Equity
2.72.11.61.00.5-0.12012201420172020
Rev, G Profit, Net Income
0.60.30.0-0.2-0.5-0.82012201420172020
Ops, Inv, Fin

cna-20201231
00000211752020FYFALSEus-gaap:OtherAssetsus-gaap:OtherAssetsus-gaap:OtherLiabilitiesus-gaap:OtherLiabilitiesP3YP1YP12MP1YP1Y00000211752020-01-012020-12-310000021175exch:XNYS2020-01-012020-12-310000021175exch:XCHI2020-01-012020-12-31xbrli:shares00000211752021-02-05iso4217:USD00000211752020-06-3000000211752020-12-3100000211752019-12-3100000211752019-01-012019-12-3100000211752018-01-012018-12-31iso4217:USDxbrli:shares0000021175us-gaap:InvestmentsMember2020-01-012020-12-310000021175us-gaap:InvestmentsMember2019-01-012019-12-310000021175us-gaap:InvestmentsMember2018-01-012018-12-310000021175us-gaap:OtherInvestmentsMember2020-01-012020-12-310000021175us-gaap:OtherInvestmentsMember2019-01-012019-12-310000021175us-gaap:OtherInvestmentsMember2018-01-012018-12-3100000211752018-12-3100000211752017-12-310000021175us-gaap:CommonStockMember2019-12-310000021175us-gaap:CommonStockMember2018-12-310000021175us-gaap:CommonStockMember2017-12-310000021175us-gaap:CommonStockMember2020-12-310000021175us-gaap:AdditionalPaidInCapitalMember2019-12-310000021175us-gaap:AdditionalPaidInCapitalMember2018-12-310000021175us-gaap:AdditionalPaidInCapitalMember2017-12-310000021175us-gaap:AdditionalPaidInCapitalMember2020-01-012020-12-310000021175us-gaap:AdditionalPaidInCapitalMember2019-01-012019-12-310000021175us-gaap:AdditionalPaidInCapitalMember2018-01-012018-12-310000021175us-gaap:AdditionalPaidInCapitalMember2020-12-310000021175us-gaap:RetainedEarningsMember2019-12-310000021175us-gaap:RetainedEarningsMember2018-12-310000021175us-gaap:RetainedEarningsMember2017-12-310000021175us-gaap:RetainedEarningsMembersrt:CumulativeEffectPeriodOfAdoptionAdjustmentMember2020-12-310000021175us-gaap:RetainedEarningsMembersrt:CumulativeEffectPeriodOfAdoptionAdjustmentMember2017-12-310000021175us-gaap:RetainedEarningsMembersrt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember2019-12-310000021175us-gaap:RetainedEarningsMembersrt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember2018-12-310000021175us-gaap:RetainedEarningsMembersrt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember2017-12-310000021175us-gaap:RetainedEarningsMember2020-01-012020-12-310000021175us-gaap:RetainedEarningsMember2019-01-012019-12-310000021175us-gaap:RetainedEarningsMember2018-01-012018-12-310000021175us-gaap:RetainedEarningsMember2020-12-310000021175us-gaap:AccumulatedOtherComprehensiveIncomeMember2019-12-310000021175us-gaap:AccumulatedOtherComprehensiveIncomeMember2018-12-310000021175us-gaap:AccumulatedOtherComprehensiveIncomeMember2017-12-310000021175us-gaap:AccumulatedOtherComprehensiveIncomeMembersrt:CumulativeEffectPeriodOfAdoptionAdjustmentMember2017-12-310000021175us-gaap:AccumulatedOtherComprehensiveIncomeMembersrt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember2019-12-310000021175us-gaap:AccumulatedOtherComprehensiveIncomeMembersrt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember2018-12-310000021175us-gaap:AccumulatedOtherComprehensiveIncomeMembersrt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember2017-12-310000021175us-gaap:AccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000021175us-gaap:AccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000021175us-gaap:AccumulatedOtherComprehensiveIncomeMember2018-01-012018-12-310000021175us-gaap:AccumulatedOtherComprehensiveIncomeMember2020-12-310000021175us-gaap:TreasuryStockMember2019-12-310000021175us-gaap:TreasuryStockMember2018-12-310000021175us-gaap:TreasuryStockMember2017-12-310000021175us-gaap:TreasuryStockMember2020-01-012020-12-310000021175us-gaap:TreasuryStockMember2019-01-012019-12-310000021175us-gaap:TreasuryStockMember2018-01-012018-12-310000021175us-gaap:TreasuryStockMember2020-12-31xbrli:pure0000021175cna:CNAFConsolidatedMembercna:LoewsMember2020-12-310000021175us-gaap:AccountingStandardsUpdate201613Member2020-01-010000021175us-gaap:RetainedEarningsMemberus-gaap:AccountingStandardsUpdate201409Membersrt:CumulativeEffectPeriodOfAdoptionAdjustmentMember2017-12-310000021175us-gaap:RetainedEarningsMemberus-gaap:AccountingStandardsUpdate201601Membersrt:CumulativeEffectPeriodOfAdoptionAdjustmentMember2017-12-310000021175srt:MinimumMember2020-01-012020-12-310000021175srt:MaximumMember2020-01-012020-12-310000021175us-gaap:FurnitureAndFixturesMember2020-01-012020-12-310000021175us-gaap:OfficeEquipmentMember2020-01-012020-12-310000021175us-gaap:ComputerSoftwareIntangibleAssetMembersrt:MinimumMember2020-01-012020-12-310000021175srt:MaximumMemberus-gaap:ComputerSoftwareIntangibleAssetMember2020-01-012020-12-310000021175us-gaap:ComputerSoftwareIntangibleAssetMember2020-01-012020-12-310000021175us-gaap:FixedIncomeSecuritiesMember2020-01-012020-12-310000021175us-gaap:FixedIncomeSecuritiesMember2019-01-012019-12-310000021175us-gaap:FixedIncomeSecuritiesMember2018-01-012018-12-310000021175us-gaap:EquitySecuritiesMember2020-01-012020-12-310000021175us-gaap:EquitySecuritiesMember2019-01-012019-12-310000021175us-gaap:EquitySecuritiesMember2018-01-012018-12-310000021175us-gaap:LimitedPartnerMember2020-01-012020-12-310000021175us-gaap:LimitedPartnerMember2019-01-012019-12-310000021175us-gaap:LimitedPartnerMember2018-01-012018-12-310000021175us-gaap:MortgagesMember2020-01-012020-12-310000021175us-gaap:MortgagesMember2019-01-012019-12-310000021175us-gaap:MortgagesMember2018-01-012018-12-310000021175us-gaap:ShortTermInvestmentsMember2020-01-012020-12-310000021175us-gaap:ShortTermInvestmentsMember2019-01-012019-12-310000021175us-gaap:ShortTermInvestmentsMember2018-01-012018-12-310000021175cna:TradingPortfolioSecuritiesMember2020-01-012020-12-310000021175cna:TradingPortfolioSecuritiesMember2019-01-012019-12-310000021175cna:TradingPortfolioSecuritiesMember2018-01-012018-12-310000021175cna:OtherInvestmentIncomeMember2020-01-012020-12-310000021175cna:OtherInvestmentIncomeMember2019-01-012019-12-310000021175cna:OtherInvestmentIncomeMember2018-01-012018-12-310000021175us-gaap:CommonStockMember2020-01-012020-12-310000021175us-gaap:CommonStockMember2019-01-012019-12-310000021175us-gaap:PreferredStockMember2020-01-012020-12-310000021175us-gaap:PreferredStockMember2019-01-012019-12-310000021175cna:SeniorNotes5750FaceAmount400DueAugust152021Memberus-gaap:SeniorNotesMember2020-01-012020-12-310000021175cna:SeniorNotes5750FaceAmount400DueAugust152021Memberus-gaap:SeniorNotesMember2020-12-310000021175cna:SeniorNotes5875FaceAmount500DueAugust152020Memberus-gaap:SeniorNotesMember2019-01-012019-12-310000021175cna:SeniorNotes5875FaceAmount500DueAugust152020Memberus-gaap:SeniorNotesMember2019-12-310000021175us-gaap:FixedIncomeSecuritiesMember2020-12-310000021175us-gaap:CorporateDebtSecuritiesMember2019-12-310000021175us-gaap:AssetBackedSecuritiesMember2019-12-310000021175us-gaap:CorporateDebtSecuritiesMembersrt:CumulativeEffectPeriodOfAdoptionAdjustmentMember2019-12-310000021175us-gaap:AssetBackedSecuritiesMembersrt:CumulativeEffectPeriodOfAdoptionAdjustmentMember2019-12-310000021175srt:CumulativeEffectPeriodOfAdoptionAdjustmentMember2019-12-310000021175us-gaap:CorporateDebtSecuritiesMember2020-01-012020-12-310000021175us-gaap:AssetBackedSecuritiesMember2020-01-012020-12-310000021175us-gaap:CorporateDebtSecuritiesMember2020-12-310000021175us-gaap:AssetBackedSecuritiesMember2020-12-310000021175us-gaap:CorporateDebtSecuritiesMember2019-01-012019-12-310000021175us-gaap:CorporateDebtSecuritiesMember2018-01-012018-12-310000021175us-gaap:AssetBackedSecuritiesMember2019-01-012019-12-310000021175us-gaap:AssetBackedSecuritiesMember2018-01-012018-12-310000021175us-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000021175us-gaap:ResidentialMortgageBackedSecuritiesMember2020-12-310000021175us-gaap:CommercialMortgageBackedSecuritiesMember2020-12-310000021175us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember2020-12-310000021175us-gaap:USTreasuryAndGovernmentMember2020-12-310000021175us-gaap:ForeignGovernmentDebtSecuritiesMember2020-12-310000021175us-gaap:RedeemablePreferredStockMember2020-12-310000021175us-gaap:FixedMaturitiesMember2020-12-310000021175us-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310000021175us-gaap:ResidentialMortgageBackedSecuritiesMember2019-12-310000021175us-gaap:CommercialMortgageBackedSecuritiesMember2019-12-310000021175us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember2019-12-310000021175us-gaap:USTreasuryAndGovernmentMember2019-12-310000021175us-gaap:ForeignGovernmentDebtSecuritiesMember2019-12-310000021175us-gaap:RedeemablePreferredStockMember2019-12-310000021175us-gaap:FixedIncomeSecuritiesMember2019-12-310000021175us-gaap:FixedMaturitiesMember2019-12-310000021175us-gaap:MortgagesMembercna:DebtToValueRatioLessThan55PercentMembercna:DebtServiceCoverageRatioGreaterThanOrEqualto1.6Member2020-12-310000021175us-gaap:MortgagesMembercna:DebtToValueRatioEqualTo55To65PercentMembercna:DebtServiceCoverageRatioGreaterThanOrEqualto1.6Member2020-12-310000021175us-gaap:MortgagesMembercna:DebtServiceCoverageRatioGreaterThanOrEqualto1.6Membercna:DebtToValueRatioGreaterThan65PercentMember2020-12-310000021175us-gaap:MortgagesMembercna:DebtToValueRatioLessThan55PercentMembercna:DebtServiceCoverageRatioBetween1.2And1.6Member2020-12-310000021175us-gaap:MortgagesMembercna:DebtToValueRatioEqualTo55To65PercentMembercna:DebtServiceCoverageRatioBetween1.2And1.6Member2020-12-310000021175us-gaap:MortgagesMembercna:DebtServiceCoverageRatioBetween1.2And1.6Membercna:DebtToValueRatioGreaterThan65PercentMember2020-12-310000021175us-gaap:MortgagesMembercna:DebtToValueRatioLessThan55PercentMembercna:DebtServiceCoverageRatioLessThanOrEqualTo1.2Member2020-12-310000021175us-gaap:MortgagesMembercna:DebtServiceCoverageRatioLessThanOrEqualTo1.2Membercna:DebtToValueRatioEqualTo55To65PercentMember2020-12-310000021175us-gaap:MortgagesMembercna:DebtServiceCoverageRatioLessThanOrEqualTo1.2Membercna:DebtToValueRatioGreaterThan65PercentMember2020-12-310000021175us-gaap:MortgagesMember2020-12-310000021175us-gaap:FairValueInputsLevel1Memberus-gaap:CorporateDebtSecuritiesMember2020-12-310000021175us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel2Member2020-12-310000021175us-gaap:FairValueInputsLevel3Memberus-gaap:CorporateDebtSecuritiesMember2020-12-310000021175us-gaap:FairValueInputsLevel1Memberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000021175us-gaap:FairValueInputsLevel2Memberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000021175us-gaap:FairValueInputsLevel3Memberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000021175us-gaap:FairValueInputsLevel1Memberus-gaap:AssetBackedSecuritiesMember2020-12-310000021175us-gaap:AssetBackedSecuritiesMemberus-gaap:FairValueInputsLevel2Member2020-12-310000021175us-gaap:FairValueInputsLevel3Memberus-gaap:AssetBackedSecuritiesMember2020-12-310000021175us-gaap:FairValueInputsLevel1Member2020-12-310000021175us-gaap:FairValueInputsLevel2Member2020-12-310000021175us-gaap:FairValueInputsLevel3Member2020-12-310000021175us-gaap:CommonStockMemberus-gaap:FairValueInputsLevel1Member2020-12-310000021175us-gaap:CommonStockMemberus-gaap:FairValueInputsLevel2Member2020-12-310000021175us-gaap:FairValueInputsLevel3Memberus-gaap:CommonStockMember2020-12-310000021175us-gaap:CommonStockMember2020-12-310000021175us-gaap:PreferredStockMemberus-gaap:FairValueInputsLevel1Member2020-12-310000021175us-gaap:PreferredStockMemberus-gaap:FairValueInputsLevel2Member2020-12-310000021175us-gaap:PreferredStockMemberus-gaap:FairValueInputsLevel3Member2020-12-310000021175us-gaap:PreferredStockMember2020-12-310000021175us-gaap:FairValueInputsLevel1Memberus-gaap:CorporateDebtSecuritiesMember2019-12-310000021175us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel2Member2019-12-310000021175us-gaap:FairValueInputsLevel3Memberus-gaap:CorporateDebtSecuritiesMember2019-12-310000021175us-gaap:FairValueInputsLevel1Memberus-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310000021175us-gaap:FairValueInputsLevel2Memberus-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310000021175us-gaap:FairValueInputsLevel3Memberus-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310000021175us-gaap:FairValueInputsLevel1Memberus-gaap:AssetBackedSecuritiesMember2019-12-310000021175us-gaap:AssetBackedSecuritiesMemberus-gaap:FairValueInputsLevel2Member2019-12-310000021175us-gaap:FairValueInputsLevel3Memberus-gaap:AssetBackedSecuritiesMember2019-12-310000021175us-gaap:FairValueInputsLevel1Member2019-12-310000021175us-gaap:FairValueInputsLevel2Member2019-12-310000021175us-gaap:FairValueInputsLevel3Member2019-12-310000021175us-gaap:CommonStockMemberus-gaap:FairValueInputsLevel1Member2019-12-310000021175us-gaap:CommonStockMemberus-gaap:FairValueInputsLevel2Member2019-12-310000021175us-gaap:FairValueInputsLevel3Memberus-gaap:CommonStockMember2019-12-310000021175us-gaap:CommonStockMember2019-12-310000021175us-gaap:PreferredStockMemberus-gaap:FairValueInputsLevel1Member2019-12-310000021175us-gaap:PreferredStockMemberus-gaap:FairValueInputsLevel2Member2019-12-310000021175us-gaap:PreferredStockMemberus-gaap:FairValueInputsLevel3Member2019-12-310000021175us-gaap:PreferredStockMember2019-12-310000021175us-gaap:CorporateDebtSecuritiesMember2019-12-310000021175us-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310000021175us-gaap:AssetBackedSecuritiesMember2019-12-310000021175us-gaap:EquitySecuritiesMember2019-12-310000021175us-gaap:CorporateDebtSecuritiesMembercna:NetRealizedInvestmentGainLossesMember2020-01-012020-12-310000021175cna:NetRealizedInvestmentGainLossesMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-01-012020-12-310000021175us-gaap:AssetBackedSecuritiesMembercna:NetRealizedInvestmentGainLossesMember2020-01-012020-12-310000021175us-gaap:EquitySecuritiesMembercna:NetRealizedInvestmentGainLossesMember2020-01-012020-12-310000021175cna:NetRealizedInvestmentGainLossesMember2020-01-012020-12-310000021175us-gaap:CorporateDebtSecuritiesMembercna:OtherRevenuesMember2020-01-012020-12-310000021175cna:OtherRevenuesMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-01-012020-12-310000021175us-gaap:AssetBackedSecuritiesMembercna:OtherRevenuesMember2020-01-012020-12-310000021175us-gaap:EquitySecuritiesMembercna:OtherRevenuesMember2020-01-012020-12-310000021175cna:OtherRevenuesMember2020-01-012020-12-310000021175us-gaap:CorporateDebtSecuritiesMember2020-01-012020-12-310000021175us-gaap:USStatesAndPoliticalSubdivisionsMember2020-01-012020-12-310000021175us-gaap:AssetBackedSecuritiesMember2020-01-012020-12-310000021175us-gaap:EquitySecuritiesMember2020-01-012020-12-310000021175us-gaap:CorporateDebtSecuritiesMember2020-12-310000021175us-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000021175us-gaap:AssetBackedSecuritiesMember2020-12-310000021175us-gaap:EquitySecuritiesMember2020-12-310000021175us-gaap:CorporateDebtSecuritiesMember2018-12-310000021175us-gaap:USStatesAndPoliticalSubdivisionsMember2018-12-310000021175us-gaap:AssetBackedSecuritiesMember2018-12-310000021175us-gaap:EquitySecuritiesMember2018-12-310000021175us-gaap:CorporateDebtSecuritiesMembercna:NetRealizedInvestmentGainLossesMember2019-01-012019-12-310000021175cna:NetRealizedInvestmentGainLossesMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2019-01-012019-12-310000021175us-gaap:AssetBackedSecuritiesMembercna:NetRealizedInvestmentGainLossesMember2019-01-012019-12-310000021175us-gaap:EquitySecuritiesMembercna:NetRealizedInvestmentGainLossesMember2019-01-012019-12-310000021175cna:NetRealizedInvestmentGainLossesMember2019-01-012019-12-310000021175us-gaap:CorporateDebtSecuritiesMembercna:OtherRevenuesMember2019-01-012019-12-310000021175cna:OtherRevenuesMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2019-01-012019-12-310000021175us-gaap:AssetBackedSecuritiesMembercna:OtherRevenuesMember2019-01-012019-12-310000021175us-gaap:EquitySecuritiesMembercna:OtherRevenuesMember2019-01-012019-12-310000021175cna:OtherRevenuesMember2019-01-012019-12-310000021175us-gaap:CorporateDebtSecuritiesMember2019-01-012019-12-310000021175us-gaap:USStatesAndPoliticalSubdivisionsMember2019-01-012019-12-310000021175us-gaap:AssetBackedSecuritiesMember2019-01-012019-12-310000021175us-gaap:EquitySecuritiesMember2019-01-012019-12-310000021175us-gaap:ValuationTechniqueDiscountedCashFlowMemberus-gaap:FixedIncomeSecuritiesMember2020-12-310000021175us-gaap:ValuationTechniqueDiscountedCashFlowMembersrt:MinimumMemberus-gaap:MeasurementInputCreditSpreadMember2020-12-310000021175us-gaap:ValuationTechniqueDiscountedCashFlowMembersrt:MaximumMemberus-gaap:MeasurementInputCreditSpreadMember2020-12-310000021175us-gaap:ValuationTechniqueDiscountedCashFlowMembersrt:WeightedAverageMemberus-gaap:MeasurementInputCreditSpreadMember2020-12-310000021175us-gaap:ValuationTechniqueDiscountedCashFlowMemberus-gaap:FixedIncomeSecuritiesMember2019-12-310000021175us-gaap:ValuationTechniqueDiscountedCashFlowMembersrt:MinimumMemberus-gaap:MeasurementInputCreditSpreadMember2019-12-310000021175us-gaap:ValuationTechniqueDiscountedCashFlowMembersrt:MaximumMemberus-gaap:MeasurementInputCreditSpreadMember2019-12-310000021175us-gaap:ValuationTechniqueDiscountedCashFlowMembersrt:WeightedAverageMemberus-gaap:MeasurementInputCreditSpreadMember2019-12-310000021175us-gaap:CarryingReportedAmountFairValueDisclosureMember2020-12-310000021175us-gaap:FairValueInputsLevel1Memberus-gaap:EstimateOfFairValueFairValueDisclosureMember2020-12-310000021175us-gaap:FairValueInputsLevel2Memberus-gaap:EstimateOfFairValueFairValueDisclosureMember2020-12-310000021175us-gaap:FairValueInputsLevel3Memberus-gaap:EstimateOfFairValueFairValueDisclosureMember2020-12-310000021175us-gaap:EstimateOfFairValueFairValueDisclosureMember2020-12-310000021175us-gaap:CarryingReportedAmountFairValueDisclosureMember2019-12-310000021175us-gaap:FairValueInputsLevel1Memberus-gaap:EstimateOfFairValueFairValueDisclosureMember2019-12-310000021175us-gaap:FairValueInputsLevel2Memberus-gaap:EstimateOfFairValueFairValueDisclosureMember2019-12-310000021175us-gaap:FairValueInputsLevel3Memberus-gaap:EstimateOfFairValueFairValueDisclosureMember2019-12-310000021175us-gaap:EstimateOfFairValueFairValueDisclosureMember2019-12-310000021175cna:FederalIncomeTaxesMember2020-01-012020-12-310000021175cna:FederalIncomeTaxesMember2019-01-012019-12-310000021175cna:FederalIncomeTaxesMember2018-01-012018-12-310000021175cna:Year2029Member2020-12-310000021175cna:Year2030Member2020-12-310000021175us-gaap:ForeignCountryMember2020-12-310000021175cna:SpecialtySegmentMember2020-12-310000021175cna:CommercialSegmentMember2020-12-310000021175cna:InternationalSegmentMember2020-12-310000021175us-gaap:CorporateAndOtherMember2020-12-310000021175cna:LifeandGroupMember2020-12-310000021175cna:LifeAndGroupNonCoreSegmentMember2020-12-310000021175cna:SpecialtySegmentMember2019-12-310000021175cna:CommercialSegmentMember2019-12-310000021175cna:InternationalSegmentMember2019-12-310000021175cna:LifeAndGroupNonCoreSegmentMember2019-12-310000021175us-gaap:CorporateAndOtherMember2019-12-310000021175cna:SpecialtySegmentMember2020-01-012020-12-310000021175cna:SpecialtySegmentMember2019-01-012019-12-310000021175cna:SpecialtySegmentMember2018-01-012018-12-310000021175cna:CommercialSegmentMember2020-01-012020-12-310000021175cna:CommercialSegmentMember2019-01-012019-12-310000021175cna:CommercialSegmentMember2018-01-012018-12-310000021175cna:InternationalSegmentMember2020-01-012020-12-310000021175cna:InternationalSegmentMember2019-01-012019-12-310000021175cna:InternationalSegmentMember2018-01-012018-12-310000021175us-gaap:CorporateAndOtherMember2020-01-012020-12-310000021175us-gaap:CorporateAndOtherMember2019-01-012019-12-310000021175us-gaap:CorporateAndOtherMember2018-01-012018-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMember2020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMember2020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMember2020-12-310000021175cna:SpecialtySegmentMembercna:WarrantyMember2020-12-310000021175cna:SpecialtySegmentMembercna:OtherMember2020-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMember2020-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2011-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2012-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2013-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2014-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2015-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2020-12-31cna:claim0000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2013-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2014-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2015-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2014-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2015-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2020-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Membercna:MedicalProfessionalLiabilityMember2016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Membercna:MedicalProfessionalLiabilityMember2017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Membercna:MedicalProfessionalLiabilityMember2018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Membercna:MedicalProfessionalLiabilityMember2019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Membercna:MedicalProfessionalLiabilityMember2020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Membercna:MedicalProfessionalLiabilityMember2017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Membercna:MedicalProfessionalLiabilityMember2018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Membercna:MedicalProfessionalLiabilityMember2019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Membercna:MedicalProfessionalLiabilityMember2020-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMember2019-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMember2020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractAccidentYear2020Membercna:MedicalProfessionalLiabilityMember2020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2012-01-012012-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2013-01-012013-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2014-01-012014-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2015-01-012015-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2016-01-012016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2017-01-012017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2018-01-012018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2019-01-012019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2020-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:MedicalProfessionalLiabilityMember2011-01-012020-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-01-012013-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-01-012014-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-01-012015-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-01-012016-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-01-012017-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-01-012018-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-01-012019-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-01-012020-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2014-01-012014-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2015-01-012015-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2016-01-012016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2017-01-012017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2018-01-012018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2019-01-012019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2020-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:MedicalProfessionalLiabilityMember2013-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2015-01-012015-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2016-01-012016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2017-01-012017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2018-01-012018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2019-01-012019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2020-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:MedicalProfessionalLiabilityMember2014-01-012020-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-01-012016-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-01-012017-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-01-012018-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-01-012019-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-01-012020-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Membercna:MedicalProfessionalLiabilityMember2017-01-012017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Membercna:MedicalProfessionalLiabilityMember2018-01-012018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Membercna:MedicalProfessionalLiabilityMember2019-01-012019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Membercna:MedicalProfessionalLiabilityMember2020-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Membercna:MedicalProfessionalLiabilityMember2016-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Membercna:MedicalProfessionalLiabilityMember2018-01-012018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Membercna:MedicalProfessionalLiabilityMember2019-01-012019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Membercna:MedicalProfessionalLiabilityMember2020-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Membercna:MedicalProfessionalLiabilityMember2017-01-012020-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-01-012019-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-01-012020-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-01-012020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMember2020-01-012020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMember2019-01-012020-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMember2018-01-012018-12-310000021175cna:SpecialtySegmentMembercna:MedicalProfessionalLiabilityMember2019-01-012019-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMember2020-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2011-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2012-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2013-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2014-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2015-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2013-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2014-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2015-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2014-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2015-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMember2019-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMember2020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractAccidentYear2020Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2012-01-012012-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2013-01-012013-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2014-01-012014-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2015-01-012015-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2016-01-012016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2017-01-012017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2018-01-012018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2019-01-012019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2020-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2011-01-012020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-01-012013-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-01-012014-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-01-012015-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-01-012016-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-01-012017-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-01-012018-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-01-012019-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-01-012020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2014-01-012014-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2015-01-012015-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2016-01-012016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2017-01-012017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2018-01-012018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2019-01-012019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2020-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2013-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2015-01-012015-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2016-01-012016-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2017-01-012017-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2018-01-012018-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2019-01-012019-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2020-01-012020-12-310000021175cna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:OtherProfessionalLiabilityandManagementLiabilityMember2014-01-012020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-01-012016-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-01-012017-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-01-012018-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-01-012019-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-01-012020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-01-012020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-01-012017-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-01-012018-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-01-012019-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-01-012020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-01-012020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-01-012018-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-01-012019-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-01-012020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-01-012020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-01-012019-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-01-012020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-01-012020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMember2020-01-012020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMember2019-01-012020-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMember2018-01-012018-12-310000021175cna:SpecialtySegmentMembercna:OtherProfessionalLiabilityandManagementLiabilityMember2019-01-012019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMember2020-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2011-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2012-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2013-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2014-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2015-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2016-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2013-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2014-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2015-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2016-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2014-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2015-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2016-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-12-310000021175cna:SuretyMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:SpecialtySegmentMember2019-12-310000021175cna:SuretyMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:SpecialtySegmentMember2020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractAccidentYear2020Member2020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2012-01-012012-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2013-01-012013-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2014-01-012014-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2015-01-012015-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2016-01-012016-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2017-01-012017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2018-01-012018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2019-01-012019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2020-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Member2011-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-01-012013-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-01-012014-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-01-012015-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-01-012016-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-01-012017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-01-012018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-01-012019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2014-01-012014-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2015-01-012015-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2016-01-012016-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2017-01-012017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2018-01-012018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2019-01-012019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2020-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2013-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2015-01-012015-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2016-01-012016-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2017-01-012017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2018-01-012018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2019-01-012019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2020-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2014-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-01-012016-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-01-012017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-01-012018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-01-012019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-01-012017-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-01-012018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-01-012019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-01-012018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-01-012019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-01-012019-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-01-012020-12-310000021175cna:SuretyMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:SpecialtySegmentMember2020-01-012020-12-310000021175cna:SuretyMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:SpecialtySegmentMember2019-01-012020-12-310000021175cna:SuretyMembercna:SpecialtySegmentMember2018-01-012018-12-310000021175cna:SuretyMembercna:SpecialtySegmentMember2019-01-012019-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMember2020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMember2020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMember2020-12-310000021175cna:CommercialSegmentMembercna:PropertyandOtherMember2020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMember2020-01-012020-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2011-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2012-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2013-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2014-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2015-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2016-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2017-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2018-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2019-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2013-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2014-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2015-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2016-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2017-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2018-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2019-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2020-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2014-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2015-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2016-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2017-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2018-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2019-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:CommercialAutoProductLineMembercna:CommercialSegmentMember2019-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:CommercialAutoProductLineMembercna:CommercialSegmentMember2020-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortDurationInsuranceContractAccidentYear2020Membercna:CommercialSegmentMember2020-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2012-01-012012-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2013-01-012013-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2014-01-012014-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2015-01-012015-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2016-01-012016-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2017-01-012017-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2018-01-012018-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2019-01-012019-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2020-01-012020-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2011-01-012020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-01-012013-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-01-012014-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-01-012015-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-01-012016-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-01-012017-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-01-012018-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-01-012019-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-01-012020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-01-012020-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2014-01-012014-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2015-01-012015-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2016-01-012016-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2017-01-012017-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2018-01-012018-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2019-01-012019-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2020-01-012020-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2013-01-012020-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2015-01-012015-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2016-01-012016-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2017-01-012017-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2018-01-012018-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2019-01-012019-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2020-01-012020-12-310000021175cna:CommercialAutoProductLineMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2014-01-012020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-01-012016-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-01-012017-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-01-012018-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-01-012019-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-01-012020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-01-012020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-01-012017-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-01-012018-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-01-012019-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-01-012020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-01-012020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-01-012018-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-01-012019-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-01-012020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-01-012020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-01-012019-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-01-012020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-01-012020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:CommercialAutoProductLineMembercna:CommercialSegmentMember2020-01-012020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:CommercialAutoProductLineMembercna:CommercialSegmentMember2019-01-012020-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMember2018-01-012018-12-310000021175cna:CommercialAutoProductLineMembercna:CommercialSegmentMember2019-01-012019-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMember2020-01-012020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2011-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2012-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2013-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2014-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2015-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2016-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2017-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2018-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2019-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2013-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2014-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2015-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2016-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2017-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2018-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2019-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2014-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2015-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2016-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2017-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2018-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2019-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:CommercialSegmentMember2019-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:CommercialSegmentMember2020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortDurationInsuranceContractAccidentYear2020Membercna:CommercialSegmentMember2020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2012-01-012012-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2013-01-012013-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2014-01-012014-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2015-01-012015-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2016-01-012016-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2017-01-012017-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2018-01-012018-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2019-01-012019-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2020-01-012020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2011-01-012020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-01-012013-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-01-012014-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-01-012015-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-01-012016-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-01-012017-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-01-012018-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-01-012019-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-01-012020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-01-012020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2014-01-012014-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2015-01-012015-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2016-01-012016-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2017-01-012017-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2018-01-012018-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2019-01-012019-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2020-01-012020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2013-01-012020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2015-01-012015-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2016-01-012016-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2017-01-012017-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2018-01-012018-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2019-01-012019-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2020-01-012020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2014-01-012020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-01-012016-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-01-012017-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-01-012018-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-01-012019-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-01-012020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-01-012020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-01-012017-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-01-012018-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-01-012019-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-01-012020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-01-012020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-01-012018-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-01-012019-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-01-012020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-01-012020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-01-012019-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-01-012020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-01-012020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:CommercialSegmentMember2020-01-012020-12-310000021175us-gaap:GeneralLiabilityMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:CommercialSegmentMember2019-01-012020-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMember2018-01-012018-12-310000021175us-gaap:GeneralLiabilityMembercna:CommercialSegmentMember2019-01-012019-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMember2020-01-012020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2011-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2012-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2013-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2014-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2015-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2016-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2017-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2018-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2019-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2013-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2014-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2015-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2016-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2017-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2018-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2019-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2014-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2015-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2016-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2017-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2018-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2019-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:CommercialSegmentMember2019-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:CommercialSegmentMember2020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortDurationInsuranceContractAccidentYear2020Membercna:CommercialSegmentMember2020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2012-01-012012-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2013-01-012013-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2014-01-012014-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2015-01-012015-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2016-01-012016-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2017-01-012017-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2018-01-012018-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2019-01-012019-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2020-01-012020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:CommercialSegmentMember2011-01-012020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-01-012013-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-01-012014-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-01-012015-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-01-012016-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-01-012017-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-01-012018-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-01-012019-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-01-012020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-01-012020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2014-01-012014-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2015-01-012015-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2016-01-012016-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2017-01-012017-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2018-01-012018-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2019-01-012019-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2020-01-012020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:CommercialSegmentMember2013-01-012020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2015-01-012015-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2016-01-012016-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2017-01-012017-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2018-01-012018-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2019-01-012019-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2020-01-012020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:CommercialSegmentMember2014-01-012020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-01-012016-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-01-012017-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-01-012018-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-01-012019-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-01-012020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-01-012020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-01-012017-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-01-012018-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-01-012019-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-01-012020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-01-012020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-01-012018-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-01-012019-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-01-012020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-01-012020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-01-012019-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-01-012020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-01-012020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:CommercialSegmentMember2020-01-012020-12-310000021175cna:WorkersCompensationMemberus-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:CommercialSegmentMember2019-01-012020-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMember2018-01-012018-12-310000021175cna:WorkersCompensationMembercna:CommercialSegmentMember2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMember2020-12-310000021175cna:InternationalSegmentMembercna:HardyMember2020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMember2020-01-012020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2011-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2012-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2013-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2014-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2015-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2016-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2017-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2018-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2019-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2013-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2014-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2015-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2016-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2017-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2014-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2015-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2016-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2017-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:InternationalSegmentMembercna:ExcludingHardyMember2019-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:InternationalSegmentMembercna:ExcludingHardyMember2020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortDurationInsuranceContractAccidentYear2020Membercna:ExcludingHardyMember2020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2012-01-012012-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2013-01-012013-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2014-01-012014-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2015-01-012015-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2016-01-012016-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2017-01-012017-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2018-01-012018-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2019-01-012019-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2020-01-012020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:ExcludingHardyMember2011-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-01-012013-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-01-012014-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-01-012015-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-01-012016-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-01-012017-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-01-012018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2014-01-012014-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2015-01-012015-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2016-01-012016-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2017-01-012017-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2018-01-012018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2020-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Member2013-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2015-01-012015-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2016-01-012016-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2017-01-012017-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2018-01-012018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2020-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Member2014-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-01-012016-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-01-012017-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-01-012018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-01-012017-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-01-012018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-01-012018-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-01-012020-12-310000021175cna:InternationalSegmentMembercna:ExcludingHardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-01-012020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:InternationalSegmentMembercna:ExcludingHardyMember2020-01-012020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:InternationalSegmentMembercna:ExcludingHardyMember2019-01-012020-12-310000021175cna:InternationalSegmentMembercna:HardyMember2020-01-012020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2012-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2013-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2014-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2015-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2016-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2017-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2018-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2019-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2013-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2014-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2015-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2016-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2017-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2018-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2019-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2014-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2015-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2016-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2017-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2018-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2019-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:InternationalSegmentMembercna:HardyMember2019-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:InternationalSegmentMembercna:HardyMember2020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortDurationInsuranceContractAccidentYear2020Membercna:HardyMember2020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2012-01-012012-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2013-01-012013-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2014-01-012014-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2015-01-012015-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2016-01-012016-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2017-01-012017-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2018-01-012018-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2019-01-012019-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2020-01-012020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2011Membercna:HardyMember2011-01-012020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2013-01-012013-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2014-01-012014-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2015-01-012015-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2016-01-012016-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2017-01-012017-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2018-01-012018-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2020-01-012020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2012Member2012-01-012020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2014-01-012014-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2015-01-012015-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2016-01-012016-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2017-01-012017-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2018-01-012018-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2019-01-012019-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2020-01-012020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2013Membercna:HardyMember2013-01-012020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2015-01-012015-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2016-01-012016-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2017-01-012017-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2018-01-012018-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2019-01-012019-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2020-01-012020-12-310000021175cna:InternationalSegmentMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2014Membercna:HardyMember2014-01-012020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2016-01-012016-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2017-01-012017-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2018-01-012018-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2020-01-012020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2015Member2015-01-012020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2017-01-012017-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2018-01-012018-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2020-01-012020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortdurationInsuranceContractsAccidentYear2016Member2016-01-012020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2018-01-012018-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2020-01-012020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2017Member2017-01-012020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2019-01-012019-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2020-01-012020-12-310000021175cna:InternationalSegmentMembercna:HardyMemberus-gaap:ShortDurationInsuranceContractsAccidentYear2018Member2018-01-012020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:InternationalSegmentMembercna:HardyMember2020-01-012020-12-310000021175us-gaap:ShortDurationInsuranceContractAccidentYear2019Membercna:InternationalSegmentMembercna:HardyMember2019-01-012020-12-310000021175cna:CNAFConsolidatedMember2020-01-012020-12-310000021175cna:AsbestosandEnvironmentalReservesMember2010-12-310000021175cna:AsbestosandEnvironmentalReservesMember2020-01-012020-12-310000021175cna:AsbestosandEnvironmentalReservesMember2019-01-012019-12-310000021175cna:AsbestosandEnvironmentalReservesMember2018-01-012018-12-310000021175cna:AsbestosandEnvironmentalReservesMember2020-12-310000021175cna:AsbestosandEnvironmentalReservesMember2019-12-3100000211752020-07-012020-09-3000000211752019-07-012019-09-3000000211752018-07-012018-09-300000021175cna:GuaranteeandIndemnificationMember2020-12-310000021175cna:GuaranteeandIndemnificationMember2019-12-310000021175us-gaap:GuaranteeObligationsMember2020-12-310000021175cna:AMinusToAPlusPlusMember2020-12-310000021175cna:BMinusToBPlusPlusMember2020-12-310000021175cna:InsolventMember2020-12-310000021175cna:SubsidiariesOfBerkshireHathawayGroupMember2020-12-310000021175cna:PaloVerdeInsuranceCompanyMember2020-12-310000021175cna:SubsidiariesofWiltonReMember2020-12-310000021175us-gaap:PropertyLiabilityAndCasualtyInsuranceSegmentMember2020-01-012020-12-310000021175cna:PercentageOfAssumedPremiumsEarnedToNetPremiumsEarnedMemberus-gaap:PropertyLiabilityAndCasualtyInsuranceSegmentMember2020-01-012020-12-310000021175cna:LongtermcareInsuranceProductLineMember2020-01-012020-12-310000021175cna:PercentageOfAssumedPremiumsEarnedToNetPremiumsEarnedMembercna:LongtermcareInsuranceProductLineMember2020-01-012020-12-310000021175cna:PercentageOfAssumedPremiumsEarnedToNetPremiumsEarnedMember2020-01-012020-12-310000021175us-gaap:PropertyLiabilityAndCasualtyInsuranceSegmentMember2019-01-012019-12-310000021175cna:PercentageOfAssumedPremiumsEarnedToNetPremiumsEarnedMemberus-gaap:PropertyLiabilityAndCasualtyInsuranceSegmentMember2019-01-012019-12-310000021175cna:LongtermcareInsuranceProductLineMember2019-01-012019-12-310000021175cna:PercentageOfAssumedPremiumsEarnedToNetPremiumsEarnedMembercna:LongtermcareInsuranceProductLineMember2019-01-012019-12-310000021175cna:PercentageOfAssumedPremiumsEarnedToNetPremiumsEarnedMember2019-01-012019-12-310000021175us-gaap:PropertyLiabilityAndCasualtyInsuranceSegmentMember2018-01-012018-12-310000021175cna:PercentageOfAssumedPremiumsEarnedToNetPremiumsEarnedMemberus-gaap:PropertyLiabilityAndCasualtyInsuranceSegmentMember2018-01-012018-12-310000021175cna:LongtermcareInsuranceProductLineMember2018-01-012018-12-310000021175cna:PercentageOfAssumedPremiumsEarnedToNetPremiumsEarnedMembercna:LongtermcareInsuranceProductLineMember2018-01-012018-12-310000021175cna:PercentageOfAssumedPremiumsEarnedToNetPremiumsEarnedMember2018-01-012018-12-310000021175us-gaap:PropertyLiabilityAndCasualtyInsuranceSegmentMembercna:PercentageOfAssumedPremiumsWrittenToNetPremiumsWrittenMember2020-01-012020-12-310000021175cna:LongtermcareInsuranceProductLineMembercna:PercentageOfAssumedPremiumsWrittenToNetPremiumsWrittenMember2020-01-012020-12-310000021175cna:PercentageOfAssumedPremiumsWrittenToNetPremiumsWrittenMember2020-01-012020-12-310000021175us-gaap:PropertyLiabilityAndCasualtyInsuranceSegmentMembercna:PercentageOfAssumedPremiumsWrittenToNetPremiumsWrittenMember2019-01-012019-12-310000021175cna:LongtermcareInsuranceProductLineMembercna:PercentageOfAssumedPremiumsWrittenToNetPremiumsWrittenMember2019-01-012019-12-310000021175cna:PercentageOfAssumedPremiumsWrittenToNetPremiumsWrittenMember2019-01-012019-12-310000021175us-gaap:PropertyLiabilityAndCasualtyInsuranceSegmentMembercna:PercentageOfAssumedPremiumsWrittenToNetPremiumsWrittenMember2018-01-012018-12-310000021175cna:LongtermcareInsuranceProductLineMembercna:PercentageOfAssumedPremiumsWrittenToNetPremiumsWrittenMember2018-01-012018-12-310000021175cna:PercentageOfAssumedPremiumsWrittenToNetPremiumsWrittenMember2018-01-012018-12-310000021175cna:SignificantCaptiveProgramMember2020-01-012020-12-310000021175cna:SignificantCaptiveProgramMember2019-01-012019-12-310000021175cna:SignificantCaptiveProgramMember2018-01-012018-12-310000021175cna:SeniorNotes5750FaceAmount400DueAugust152021Member2020-12-310000021175cna:SeniorNotes5750FaceAmount400DueAugust152021Member2019-12-310000021175cna:SeniorNotes3.950faceamountof550dueMay152024Member2020-12-310000021175cna:SeniorNotes3.950faceamountof550dueMay152024Member2019-12-310000021175cna:SeniorNotes4.500faceamountof500dueMarch12026Member2020-12-310000021175cna:SeniorNotes4.500faceamountof500dueMarch12026Member2019-12-310000021175cna:SeniorNotes3.450faceamountof500dueAugust152027Member2020-12-310000021175cna:SeniorNotes3.450faceamountof500dueAugust152027Member2019-12-310000021175cna:SeniorNotes3.900faceamountof500dueMay12029Member2020-12-310000021175cna:SeniorNotes3.900faceamountof500dueMay12029Member2019-12-310000021175cna:SeniorNotes2050FaceAmountOf500DueAugust152030Member2020-12-310000021175cna:SeniorNotes2050FaceAmountOf500DueAugust152030Member2019-12-310000021175us-gaap:SubordinatedDebtMember2020-12-310000021175us-gaap:SubordinatedDebtMember2019-12-31cna:extensionTerm0000021175us-gaap:PensionPlansDefinedBenefitMember2019-12-310000021175us-gaap:PensionPlansDefinedBenefitMember2018-12-310000021175us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember